It is known to provide heat exchangers on electrical components and assemblies to dissipate the heat generated by the electrical components. Typically, such heat exchangers are provided either in the form of a passive heat sink or an active heat sink. Passive heat sinks rely upon natural convection, radiation and conduction to dissipate the heat, while active heat sinks dissipate the heat to a coolant that is flowed over or through the heat sink by a pump or fan, or in the case of some moving vehicles, by the relative velocity between the vehicle and the fluid, such as air, in which the vehicle is traveling.
Typically, the goal of such heat exchangers is to maintain electrical components within their normal operating temperature range, which is the temperature range that allows sustained operation of the electrical components within specifications without reducing the required operating life. An additional goal of such heat exchangers may be to ensure that, during an abnormal operating condition, the electrical components never exceed their maximum operating temperature range, which is the temperature range that allows a component to perform its required function without reducing the required operating life of the component as long as there are limited number of occurrences of the component operating at the maximum operating temperature range, with each occurrence being for a limited time period.
A primary advantage of passive heat sinks is their simplicity because they require no fans, pumps, ducts, conduits, or other means for flowing a coolant over or through the passive heat sink. One problem with passive heat sinks is that they may experience difficulty in providing a sufficient heat rejection rate to adequately cool certain electrical components, such as power electronics including motor drives, power converters, and power inverters.
A primary advantage of active heat sinks is that they can provide more effective heat dissipation in comparison to passive heat sinks and thus are often more suitable to those electrical components that require a high rate of heat dissipation. One problem with active cooling is that if a fan or pump fails, a loss of cooling will occur and may potentially damage the electrical components through overheating.
In some environments, such as in an aircraft, it is not uncommon for there to be a requirement that EMI shielding be provided for the electrical components and/or that each of the electrical components in the assembly be mounted in an enclosed interior cavity that restricts and/or prevents active air flow over the electrical components. These requirements can complicate the problem of dissipating heat generated by the electrical components.